New Scientist Environment <http://environment.newscientist.com/>
Cleaner skies explain surprise rate of warming
* 09 July 2008
* From New Scientist Print Edition. Subscribe
<http://environment.newscientist.com/subscribe.ns?promcode=nsenvarttop>
and get 4 free issues
GOODBYE air pollution and smoky chimneys, hello brighter days. That's
been the trend in Europe for the past three decades - but unfortunately
cleaning up the skies has allowed more of the sun's rays to pierce the
atmosphere, contributing to at least half the warming that has occurred.
Since 1980, average air temperatures in Europe have risen 1 °C: much
more than expected from greenhouse-gas warming alone. Christian
Ruckstuhl of the Institute for Atmospheric and Climate Science in
Switzerland and colleagues took aerosol concentrations from six
locations in northern Europe, measured between 1986 and 2005, and
compared them with solar-radiation measurements over the same period.
Aerosol concentrations dropped by up to 60 per cent over the 29-year
period, while solar radiation rose by around 1 watt per square metre
(/Geophysical Research Letters/, DOI: 10.1029/2008GL034228
<http://dx.doi.org/10.1029/2008GL034228>). "The decrease in aerosols
probably accounts for at least half of the warming over Europe in the
last 30 years," says Rolf Philipona, a co-author of the study at
MeteoSwiss, Switzerland's national weather service.
The latest climate models are built on the assumption that aerosols have
their biggest influence by seeding natural clouds, which reflect
sunlight. However, the team found that radiation dropped only slightly
on cloudy days, suggesting that the main impact of aerosols is to block
sunlight directly.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.amrad.org/pipermail/tacos/attachments/20080711/ad062ed9/attachment.htm
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/gif
Size: 4675 bytes
Desc: not available
Url : http://www.amrad.org/pipermail/tacos/attachments/20080711/ad062ed9/attachment.gif